Objective: The objective of the proposed research is to investigate the expression of the same sequences of DNA in simian virus 40 (SV40)-nucleoprotein complex and in 3T3 (mouse) cells transformed by SV40 in order to investigate the mode of regulation of expression of SV40 DNA in SV3T3 chromatin and in SV40-nucleoprotein complex by proteins. Methods: 1. The expression of the same sequences of DNA in SV40- nucleoprotein complex and in SV3T3 cells will be determined by RNA/DNA hybridization methods. 2. The regulation of expression of SV40 DNA in SV3T3 chromatin by chromosomal proteins will be investigated by studying the effect of deletion of certain nonhistone protein fractions and alterations in the order of reassociation of different chromosomal proteins during reconstitution of chromatin on the transcription of SV40 DNA from SV3T3 chromatin. 3. The possible regulation of the expression of the genome in SV40-nucleoprotein by viral internal protein shall also be investigated by studying the specific properties of the viral internal proteins binding to the viral DNA. 4. The presence of protein(s) which show(s) strong affinity for SV40 DNA in SV3T3 chromatin but not in 3T3 chromatin shall be investigated by DNA-affinity chromatography.